Set of Commands Used in Linux and their Meaning

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Learning Linux commands is one of the main concerns for any Linux beginner. Although, the improvement in GUI has made it possible to accomplish almost everything with a graphical interface the fact is you still need to know the Linux command line to get the most out of it. Here’s a Linux command quick reference guide along with meanings (what they do).

ls (Synopsis: s [options] [names])

Lists the contents of a directory.

mkdir (Synopsis: mkdir [OPTION] DIRECTORY)

Creates a (or more than one) new directory.

cp (Synopsis: cp [OPTION]… SOURCE… DIRECTORY)

Copy source to destination (to copy files)

mv (Synopsis: mv [OPTION]… SOURCE… DIRECTORY)

Move/rename files or directories

cal (synopsis: cal [-3jmy] [[month] year])

Displays a calendar

whoami (Synopsis: whoami [OPTION])

Displays the user id of the current user.

Tree (Synopsis: Tree [-OPTIONS])

Lists the contents of directories in a tree structure.

cat (Synopsis: cat [OPTION] [FILE])

Concatenate files.

uptime (Synopsis: Uptime /Uptime [-V])

Displays how long the system has been running.

pwd (Synopsis: pwd [OPTIONS])

Prints the name of the current directory

df (Synopsis: df [OPTION] ..[FILE])

displays disk space usage data

whereis (Synopsis: whereis [ -bmsu ] [ -BMS directory… -f ] filename)

Find the binary, source for specified files.

man (Synopsis: man [options] [section] [title])

Display the on-line reference manual.

Kill (Synopsis: kill [ -signal | -s signal ] pid)

Sends a signal to terminate a (or multiple) process IDs.

mount (Synopsis: mount [-lhV])

Mounts a file system.

grep (Synopsis: grep [OPTIONS] PATTERN [FILE…])

Searches for files matching a regular expression pattern.

chmod (Synopsis: chmod [OPTION]… MODE[,MODE]… FILE)

Changes the file mode bits.

ln (Synopsis: ln [OPTION]… TARGET)

Makes links between files.

top (Synopsis: top [options])

Displays the currently running Linux tasks.

cron (Synopsis: cron [-f] [-l] [-L loglevel])

Execute scheduled commands.

sudo (Synopsis: sudo [options] [command] )

Run a command as another user.

hostname (Synopsis: hostname [option] [nameofhost])

Display/set the host name of the system.

ssh (Synopsis: ssh [options] hostname [command])

A program to log into a remote machine and executing command on the remote machine.

rm (Synopsis: rm [OPTION]… FILE)

Remove specified files or directories.

ps (Synopsis: ps [Options])

Displays a snapshot of the current running processes.

locate (Synopsis: locate [options] pattern)

Search and displays file names matching the specified pattern

find (Synopsis: find [pathnames] [conditions])

Performs a search for files in a directory hierarchy.

w (Synopsis: w[Options] [user])

Displays which user is logged in and what they are doing.

finger (Synopsis: finger [options] users)

Displays information about the system users.

ping (Synopsis: ping [options] host)

A common tool to check if a remote system is online and responding.

gpg (Synopsis: gpg [options] command [options])

Encrypt and decrypt information using the OpenPGP encryption and signing tool.

atd (Synopsis: atd [options])

Run jobs that are queued for later execution

bash (Synopsis: bash [options] [file])

The GNU Bourne-Again Shell.

chattr (Synopsis: chattr [options] mode files)

Modify file attributes on Linux second extended file system.

chown (Synopsis: chown [OPTION]… [OWNER][:[GROUP]] FILE)

Change the ownership of files.

cksum (Synopsis: cksum [files] )

Displays CRC checksum and byte counts for a file.

clear (Synopsis: clear)

Clears the terminal display.

cmp (Synopsis: cmp [options] file1 file2 [skip1 [skip2]] )

Compares two files byte by byte.

date (Synopsis: date [OPTION] [+FORMAT])

Display/set the system date and time.

du (Synopsis: du [options] [directories])

Displays a summary of disk usage of each file, recursively for directories.

expr (Synopsis: expr [EXPRESSION])

Evaluates an expression and displays the result.

ftp (Synopsis: ftp [options] [hostname])

The internet file transfer tool to transfer files to and from a remote host.

halt (Synopsis: halt [options])

Shutdown or reboot the system.

iptables (Synopsis: iptables command [options])

A tool for IPv4 packet filtering. Used to setup and maintain the tables of IP packet filter rules in the Linux kernel.

join (Synopsis: join [options] file1 file2)

This command joins the lines of two files matching on a common field.

last (Synopsis: last [options] [user] [ttynumber])

Display a list of last logged in users.

netstat (Synopsis: netstat [options] [delay])

Displays information about the Linux networking subsystem.

passwd (Synopsis: passwd [options] [LOGIN])

Change the password for any user account.

pinky (Synopsis: pinky [options] [users])

A light weight finger program that displays user information.

stat (Synopsis: stat [option] file )

Prints file (or file system) status.